Morphologic analysis remains an essential tool for visualizing the spatial relationships of different cell types and cellular components in the GI tract. The unique feature of the Cell and Molecular Pathology Core, under the direction of Drs. Jiri Mestecky, Robinna Lorenz, and Lesley Smythies, is the expertise it provides to participating investigators on the structural biology of the GI tract. The Structure Characterization Unit and the Structure interaction Unit are closely related in techniques to be provided but distinct in their approach. Whereas the Structure Characterization Unit under Dr. Mestecky will focus on whole structure morphology, the Structure interaction Unit under Dr. Lorenz will focus on the detection of how mucosal structures and cells interact, such as the "cross-talk" between the epithelium and lamina propria stromal (mesenchymal) cells. The primary function will be the morphologic analysis of mucosal tissues to assist and train Base Grant investigators and their collaborators in the morphologic analysis of the GI tract. The Core also will serve as an important resource for rapid processing of tissue specimens and for providing investigators with newly developed methods/protocols and reagents for labeling tissue sections. Finally, the Core will have the unique function of providing investigators access to purified human mucosal cells. Thus, the purpose of Core 2 will be (1) to provide newly developed methods for training Base Grant investigators in the morphologic analysis of the GI tract and (2) to provide purified primary human mucosal cells invaluable in elucidating the interactions between mucosal cells and commensal bacteria, pathogenic organisms or their products. These functions are presently not readily available to many of the Core members. Delays are common in processing tissues at other on-campus facilities due to heavy user volumes, and the standard rates are high.